Bibcode
Beck, C.
Bibliographical reference
Astronomy and Astrophysics, Volume 480, Issue 3, 2008, pp.825-838
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3
2008
Journal
Citations
48
Refereed citations
40
Description
Aims:I deduced a 3D sunspot model that is in full agreement with
spectropolarimetric observations, in order to address the question of a
possible penumbral heating process by the repetitive rise of hot flow
channels. Methods: I performed inversions of spectropolarimetric
data taken simultaneously in infrared (1.5 μm) and visible (630 nm)
spectral lines. I used two independent magnetic components inside each
pixel to reproduce the irregular Stokes profiles in the penumbra and
studied the averaged and individual properties of the two components. By
integrating the field inclination to the surface, I developed a 3D model
of the spot from inversion results without intrinsic height information.
Results: I find that the Evershed flow is harbored by the weaker
of the two field components. This component forms flow channels that
show upstreams in the inner and mid penumbra, continue almost
horizontally as slightly elevated loops throughout the penumbra, and
finally bend down in the outer penumbra. I find several examples where
two or more flow channels are found along a radial cut from the umbra to
the outer boundary of the spot. Conclusions: I find that a model
of horizontal flow channels in a static background field is in good
agreement with the observed spectra. The properties of the flow channels
correspond very well to the moving tube simulations of Schlichenmaier et
al. (1998, A&A, 337, 897). From the temporal evolution in intensity
images and the properties of the flow channels in the inversion, I
conclude that interchange convection of rising hot flux tubes in a thick
penumbra still seems a possible mechanism for maintaining the penumbral
energy balance.
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